ModifyingDarkMatterFreezeOutat theElectroweakPhaseTransition - - PowerPoint PPT Presentation

Modifying
Dark
Matter
Freeze
Out
at the
Electroweak
Phase
Transition

Andrew
Long

University
of
Wisconsin,
Madison

with
D.J.H.
Chung,
S.
Tulin,
L.T.
Wang EWPT ρφ expansion Hfo DM
f.o. Ω Tuning ρΛ

Cosmology
&
 Astronomy Collider
& (In)Direct
Search

Will
they match?

[Kolb & Wolfram, 1980]

• Tune CC against SM Higgs vacuum energy

[Barrow, 1982]

• Anisotropic expansion boosts relic abundance

[McDonald, 1990]

• Decaying massive particles dominate ρ at freeze out

[Kamionkowski & Turner, 1990] - “Thermal Relics: Do we know their abundance?” [Joyce, 1997]

• Kination dominated scalar field modifies H at EWPT

[Salati, 2003]

• Quintessence modifies H at freeze out

[Profumo & Ullio, 2003]

• Kination dom. quintessence modifies χ0 abundance

[Megevand & Sanchez, 2008] - Entropy production at first order PT & dilutes relic [Wainwright & Profumo, 2009] - Entropy production saves SUSY models

Suppose
they don’t
match!

What
went
wrong?
‐‐
We
should
not
assume
radiation
dominates
at
freeze
out

Andrew Long - 3

Additional
contribution
to ρ from
scalar
&
tuned
cosmological
constant

Larger
H Γ ∼ H
earlier Larger ΩDM

Suppose
they don’t
match!

What
went
wrong?
‐‐
We
should
not
assume
radiation
dominates
at
freeze
out

Andrew Long - 4

Mismatch signals
new
physics
in
Higgs sector
&
CC
tuning

Suppose
they don’t
match!

What
went
wrong?
‐‐
We
should
not
assume
radiation
dominates
at
freeze
out Additional
contribution
to ρ from
scalar
&
tuned
cosmological
constant

Larger
H Γ ∼ H
earlier Larger ΩDM

Andrew Long - 4

Cosmological
History

BBN (ρr dom.)

1 G e V 1 G e V 1 G e V

Standard Cosmology Modified Cosmology freeze
out during ρr domination freeze
out while
H
boosted EWPT supercooling ρφ + ρΛ ∼ ρr phase
transition completes

Andrew Long - 5

1)

Calculate
thermal
effective
potential
VT(φ)‐‐free
energy
 density
of
a
gas
at
temperature
T
coupled
to
condensate
φ 2)

Tune
CC
against
scalar
vacuum
energy
at
zero
temperature 3)

Calculate ΔH/H
as
a
function
of
temperature 4)

(Embed
scalar
sector
into
a
model
of
DM
with
freeze
out


• ccuring
before
or
during
EWPT
when
ΔH/H
is
maximal)

H
at
EWPT
&
Tuning
CC

The
Calculation:

Andrew Long - 6

Second
Order
PT
&
SM

Standard
Model
phase
transition Why
is ΔH/H
so
small?

• Same
parameters
control
vacuum

energy
&
temperature:

V(T)/T4
∼
O(1)

• Hard
to
beat
g*
∼
100
suppression

solution
=
 supercooling tuning
CC

Andrew Long - 7

c1
~
ht

2
+
g2

• The
Hubble
parameter
receives
a
larger
correction
when

the
universe
is
suspended
in
a
metastable
phase

• Then,
ΔH/H
∼
V/T4
grows
at
T
drops
• Real
singlet
extension
admits
a
1PT

First
Order
PT
&
xSM

[Ramsey-Musolf, et. al., 2007]

gauge singlet

at
T∼Tc,
metastable minimum
here

tuning
CC

Andrew Long - 8

(1) Symmetry restored at high temperature

Andrew Long - 9

(2) Origin becomes metastable below critical temperature

Andrew Long - 9

(3) During supercooling, ΔH/H grows like 1/T4 in metastable phase

Andrew Long - 9

freeze out now!

(4) At a lower temperature the PT completes

Andrew Long - 9

1) 
DM
relic
abundance
can
be
enhanced
by
O(10%)
if
freeze
out
occurs
during
a first
order
electroweak
phase
transition 2) 
Favors:

a) Extended
scalar
sector b) Low
temperature
phase
transition
&
high
temperature
freeze
out
(10s
GeV) heavy
dark
matter
favored
by
PAMELA c) Sufficient
supercooling


















strongly
first
order
phase
transitions
allow
for interesting
physics
such
as
baryogenesis
and
gravity
waves

3) 
Mismatch
between
cosmological
and
collider‐inferred relic
abundance
may
provide
evidence
for
a
link
between
dark matter,
the
Higgs
sector,
and
tuning
of
the
cosmological
constant

Summary
‐‐
What
to
do
if

Andrew Long - 10

EWPT ρφ expansion Hfo DM
f.o. Ω Tuning ρΛ